Acute Kidney Injury Warning Stage

  • 1st Revision: Isobel Lester
  • 2nd Revision: Tamsin Rose
  • 3rd Revision: Sophia Bradshaw

Short Explainer Video

What is Acute Kidney Injury?

Acute kidney injury (AKI) occurs when your kidneys suddenly stop functioning as normal. This can be a result of complications caused by other serious diseases.

The damage can range from minor loss of kidney function to complete kidney failure. This type of kidney damage is most common in older people who are suffering from other health conditions that also affect the kidneys. 

If AKI is detected early, the efficacy of treatment can be maximised and this can result in reduced mortality rates.

However, failure to provide immediate treatment can cause an accumulation of abnormal levels of salts and chemicals in the body, affecting the function of other organs. 

In the case of complete kidney impairment, it may be necessary to use a dialysis machine, as failure to do so can lead to death.(1)

Studies suggest that up to 30% of these could have been prevented with proper care and treatment.(2) AKI must be taken seriously even if it does not progress to complete kidney failure. It affects the entire body, alters how some drugs are metabolised by the body, and may exacerbate some existing illnesses.

Therefore, it is really important to monitor kidney function if you have symptoms of AKI or are in a high-risk group.(1)

High-risk groups include:

  • People aged over 65 years old
  • People with other kidney diseases such as chronic kidney disease
  • People with other medical conditions such as heart failure, liver disease, diabetes, infection, or sepsis
  • Those taking the following medicine: Non- steroidal anti-inflammatory drugs (NSAIDs) (e.g. ibuprofen), blood pressure managing drugs (e.g. ACE inhibitors or diuretics), aminoglycosides (antibiotics)
  • People suffering from dehydration or blockage of the urinary tract   


The symptoms of AKI are(1):

  • Feeling/being sick
  • Diarrhea
  • Subsequent dehydration 
  • Peeing less than usual
  • Confusion
  • Drowsiness


Most cases of AKI are caused by reduced blood flow to the kidneys, usually in people with pre-existing health condition. AKI can occur due to the following(1):

  • Decreased blood flow or low blood volume as a result of heart failure, liver failure, sepsis, severe dehydration, etc.
  • Inflammation/blockage/damage to blood vessels within the kidneys.
  • Certain medications or liquid dyes used in radiography can affect the blood supply.
  • An enlarged prostate, kidney stones, or a tumor in nearby tissues such as the ovary or bladder.

Diagnosis and Treatment

Diagnosing AKI

A blood test to measure your levels of creatinine, a chemical waste product produced by muscles, is generally used to diagnose AKI. If the level of this waste has doubled, kidney function has halved and AKI has developed.

There is no full-blown AKI if the creatinine level has increased but not doubled, but action must be taken to avoid AKI. You may also be asked to provide a urine sample or have an ultrasound of your kidneys to check for any blockages, such as the presence of an enlarged prostate or bladder tumour which could be the cause of your symptoms.

Doctors will also ask more about your symptoms, other medical conditions, and medications taken to investigate the underlying causes.(1)


Treatment for AKI depends on what caused it to occur. Most people need to stay in the hospital during treatment and until their kidneys have recovered.

While you are treated for the problem that caused your AKI, you may also have treatments to prevent problems that can make it harder for your kidneys to heal. Some possible treatments include(3)

  • Hydration and electrolyte therapy to maintain the optimum levels of fluid
  • Using a urinary catheter to drain the bladder if there is a blockage
  • Antibiotics (if you have an infection)
  • Stop taking certain medications
  • Follow a kidney-friendly diet  
  • Temporary haemodialysis 


AKI is difficult to predict or prevent because it occurs suddenly. However, taking good care of your kidneys can help prevent AKI, chronic kidney disease, and kidney failure/end-stage kidney disease (ESRD).(1,3)

Here are some tips to help prevent AKI:

  • Medicines
    Take all prescription medications as your doctor tells you to, do not exceed the recommended dose.
  • Monitoring
    • Regular blood tests should be taken if you are at high risk of developing AKI or start a new medication.
    • Check how much urine you pass
  • Limit alcohol
    Consume no more than 14 units, which is the equivalent of six glasses of wine, per week.
  • Healthy weight and lifestyle
    • Minimise salt and fat in your diet
    • Try to exercise for 30 minutes at least five days a week
    • Give up smoking


AKI is a sudden onset of abnormal kidney function. It can occur due to reduced blood flow to the kidneys, however, other factors such as inflammation in the kidneys, certain medications and low blood volume can also cause AKI. With early diagnosis, treatment efficacy can be maximised. However, by taking care of your kidneys through a healthy lifestyle, AKI can be prevented. 


What does the acute kidney warning stage mean?

The result of AKI tests (comparing patient's current creatinine within clinical context against baseline creatinine) is called "AKI Warning Stage".(4)

Does acute kidney injury have stages? What are the stages of AKI?

AKI has 3 stages and is based on your serum creatinine concentration.(4)

  • Stage 1: Current creatinine ≥1.5 x baseline level (or creatinine rise >26 mol/L 48 hrs)
  • Stage 2: Current creatinine ≥2 x baseline level
  • Stage 3: Current creatinine ≥3 x baseline level (or creatinine 1.5 x baseline and >354 mol/L)

What are the warning signs of acute kidney failure?

Diarrhea and vomiting, low blood pressure with lightheadedness, and passing only small volumes of urine.(4)

Does acute kidney injury go away?

AKI is often reversible if it is detected and treated quickly. 

How long does it take to recover from acute kidney injury?

This depends on its severity. In some cases, AKI can resolve in a couple of days with fluid and antibiotics. In other cases, the illness that affects the kidneys and the rest of the body may be so severe that recovery takes two or three weeks or even longer.(5)

What does AKI Stage 0 mean?

There are some changes in serum creatinine concentration, but they are not significant or above ≥1.5 x baseline level. You should regularly monitor kidney function at this stage to prevent further deterioration of AKI.


  1. Acute kidney injury [Internet]. NHS choices. NHS; [cited 2022May19].
  2. Millett D. Pathology labs to send acute kidney injury alerts direct to practices [Internet]. GPonline. GP; 2016 [cited 2022May19].
  3. Acute kidney injury (AKI) [Internet]. American Kidney Fund. 2022 [cited 2022May19].
  4. Think Kidneys [Internet]. NHS choices. NHS; [cited 2022May19].
  5. National Kidney Federation. [cited 2022May19].
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Yuting Jiang

Master of Science in Pharmacy - UCL (University College London)
Dynamic Master of Pharmacy student driven by a passion for providing high-quality patient care. Engaged in rigorous programmes of professional development, refining a myriad of skills, including data, analytical, and numerical. Gained excellent multi-lingual communication skills used to great effect in developing strong, multidisciplinary relationships and in the confident presentation of research findings both verbally and in writing.

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